The goal of this project is the prevention or control of trachoma, the world's most important cause of blindness. The goal is sought through better understanding of the pathogenesis and epidemiology of the disease and by attempts to modify the elementary body particle of trachoma to obtain a more effective immunizing antigen. The isolation, identification and chemical characterization of type specific protective antigens will be attempted, as will the elimination from vaccines of antigens associated with the development of hypersensitivity. A micro immunofluorescence test which measures type specific antibody in serum and eye secretions will be utilized in studies of pathogenesis and epidemiology. Classification of TRIC and related genital chlamydial organisms will be continued, using immunological (immunofluorescence) and biological (pathogenesis for the monkey eye) tests. Clinical, epidemiological and laboratory studies of genital TRIC organisms and related chlamydiae will be directed at determining the importance of these agents in causing disease, both in trachoma endemic Taiwan and nonendemic United States.